Thread: Insulate or heat a crawspace?

I have a crawspace that is insulated, but who built the house put the insulation with the paper down, now it falling down. Should i tear all the insulation out and put heat in the crawl or should i put new insulation in. Its a 26x26 with a dirt floor

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Originally Posted by Brent Schlosser

I have a crawspace that is insulated, but who built the house put the insulation with the paper down, now it falling down. Should i tear all the insulation out and put heat in the crawl or should i put new insulation in. Its a 26x26 with a dirt floor

Put a moisture barrier(plastic) down on the dirt wall to wall in the crawl. Do not heat the crawlspace. I would replace the insulation with unfaced insulation, I prefer this in crawlspaces over faced insulation.

The vapor barrier on the insulation (paper side) should face the warm side of the area it is insulating.

Originally Posted by Scott Patterson

The vapor barrier on the insulation (paper side) should face the warm side of the area it is insulating.

Sounds like a lot of work flipping it over every spring and fall

New Light in Crawlspaces - Building Science
BSI-009: New Light In Crawlspaces — Building Science Information

Originally Posted by Raymond Wand

New Light in Crawlspaces - Building Science
BSI-009: New Light In Crawlspaces — Building Science Information

That's a nice article. My advice is similar. Do it right. More money now, but will pay you back.

Unless your crawlspace has significant mositure issues, I would recommend converting it to a sealed and conditioned crawlspace. It will typically cost less than insulating the floors and will be more energy efficient than a standard vented crawlspace. This involves insulating the perimeter foundation walls and joist band, installing a good vapor barrier, sealing off existing foundation vents, and installing an HVAC vent or two in the crawlspace. Also with a sealed and conditioned crawlspace insulating duct work and water supply pipes is not required.

I say the same thing as Trent. The crawl space conditioning done properly allows less ventilation so you can close the vents and retain the heat that's normally lost. This can make large improvements in comfort and efficiency of the home. Doing it right is the most difficult part but worth doing it right the first time.

Yep, I also agree with Trent. Unless there's absolutely no way to rid the area of moisture, insulating and conditioning the crawlspace is the way to go.

If your not going to include the crawl in the building envelope, make sure its well ventilated in addition to installing vapor barrier on floor and fixing underfloor insulation.

I thought DIY inquiries to this forum were supposed to be thinly veiled, as in "I ran into a situation with a crawlspace" or "I have a friend with a crawlspace", etc. Since when the sudden tolerance?

Originally Posted by Lon Henderson

That's a nice article. My advice is similar. Do it right. More money now, but will pay you back.

Is anyone aware of a typical payback period or of an applicable building science study?

Too many variables to give an accurate assessment.

Originally Posted by Dale Trach

Is anyone aware of a typical payback period or of an applicable building science study?

Here are the last house I tested results. 2000 sqft, 80% Natural Gas Furnace. The crawlspace conditioning with R-11, sealed plastic, and minor duct sealing cost $5000. This will save 20.6% on therms and 10.8% on KWH.

These results will vary based on climate, heating type, fuel cost, and condition of the rest of the home. For this house it's about a 13yr payback. The natural gas here is relatively cheap compared to oil or propane. But as fuel cost rise or if they go down (yea right) this will change. There is an additional benefit from comfort improvement and reduction in moisture. If your in a Radon area that's something that can also be included easily in to this.

Great Artical Raymond, Helps me to better explan common situations in my area, A lot people have not clue what damage an improper installation can cause.

Reality is that it doesn't make a rat's butt's difference if the paper is facing up or not. The supposed vapor barrier is so porous as to make it not worth worrying about. If you have some down, put it up any way that's easy. If you really want to freak about the paper on the rest of it, take a knife and score is. Are sealed crawls better? Sure. But doing it right requires some serious effort.
If you want to research it, try: buildingscience.com. Joseph Lstiburek is the man.

JL Mathis

Originally Posted by Dale Trach

Is anyone aware of a typical payback period or of an applicable building science study?

The intangibles are impossible to quantify, but a properly conditioned crawlspace eliminates the future possible expense of repairs from mold or wood rot, etc. A sealed floor in a crawlspace makes it difficult for termites too.

Originally Posted by Mike Locurcio

I thought DIY inquiries to this forum were supposed to be thinly veiled, as in "I ran into a situation with a crawlspace" or "I have a friend with a crawlspace", etc. Since when the sudden tolerance?

Speaking for myself, of course, I am more interested if the DIY question is interesting. There seems to be some self regulation. An uninteresting or stupid DIY question gets little to no response.

Originally Posted by Lon Henderson

The intangibles are impossible to quantify, but a properly conditioned crawlspace eliminates the future possible expense of repairs from mold or wood rot, etc. A sealed floor in a crawlspace makes it difficult for termites too.

In North Carolina the liner must terminate a minimum of 3" below the top of the masonry for termite inspection, just because almost nothing stops termites.